1. Field of the Invention
The embodiments discussed herein relate to an offset correction circuit and a transconductance proportional current generation circuit.
2. Background of the Related Art
In a differential amplifier circuit, imbalance is usually generated in electric current that flows in the circuit, due to mismatch of characteristics of differential pair transistors and characteristics of active loads connected to the differential pair transistors, and this electric current imbalance results in generation of offset voltage. When the offset voltage is high, the offset voltage becomes an error factor and sometimes affects circuit operation, and therefore the offset voltage is corrected.
As a past technology, there is a proposed technology which utilizes metal-oxide-semiconductor field-effect transistors (MOSFETs) that operate as a differential input pair and a constant current source having a negative temperature coefficient for supplying constant current to the MOSFETs, thereby reducing temperature drift of the offset voltage.
See, for example, Japanese Laid-open Patent Publication No. 5-291845.
In the differential amplifier circuit of the past, an offset voltage correction current source is located to generate offset correction voltage on the basis of a current value that flows in the current source, in order to correct the offset voltage.
However, the offset correction voltage is dependent on temperature and thus changes as the temperature changes, making it difficult to correct the offset voltage highly accurately.